In vehicles which are at least partially electrically driven, electrical energy stores are used in order to store the electrical energy for the electric motor which assists the drive or serves for driving. In latest-generation vehicles, what are known as lithium-ion batteries are used for this purpose. Lithium-ion batteries are distinguished, amongst other things, by high energy densities and an extremely low level of self-discharging. Lithium-ion battery cells have at least a positive and a negative electrode (cathode and, respectively, anode), these electrodes being able to reversibly insert (intercalation) or extract (deintercalation) lithium ions (Li+).
FIG. 1 shows how individual battery cells 10 can be combined to form battery modules 12 and then to form batteries 14. This is performed by connecting the poles of the battery cells 10 in parallel or in series (not illustrated). In this case, a battery module 12 or a battery 14 comprises, by definition, at least two battery cells 10, wherein the terms battery 14 and battery module 12 are often used synonymously. The electrical voltage of a battery 14 is, for example, between 120 and 600 volts DC.
Various influences can influence the service life or the reliability of a lithium-ion battery. Said influences include, firstly, electrical influences such as excessively high currents or voltages, temperature influences, and also mechanical influences. Battery cells of which the housings are composed of a solid aluminum or steel sheet are inherently dimensionally stable and withstand relatively small knocks without mechanical deformation. However in the event of the battery-operated vehicle being involved in an accident, the housing of the battery and therefore of the battery cells may also be permanently and considerably deformed. In this situation, there is a risk of, for example, parts of the vehicle body coming into contact with a battery pole and therefore endangering occupants and rescue personnel.
DE 10 2009 050 996 A1 discloses an apparatus and a method for severing the connection lines between at least two energy sources (for example battery cells) within an energy storage device (for example a battery). The lines are severed by a propellant which is discharged, for example, after the evaluation of a crash signal. Severing the lines within the battery interrupts the internal flow of current, as a result of which the battery can no longer be short-circuited from the outside.
U.S. Pat. No. 5,760,488 A is concerned with providing a vehicle with a fuel cell—or battery-fed energy supply system. Said vehicle is equipped with an insulation monitoring means for protecting against high contact voltages.